for a rainy day

基本解释

Householders cannot rely on a ready supply of credit—or on government safety nets—so must save hard for a rainy day.
家庭儲戶不能依賴現成的貸款供應或政府所提供的安全網，因此他們必須未雨綢繆地努力儲蓄。
Many of those people have since returned to Hong Kong, their home, and have kept those second passports in the drawer for a rainy day.
在廻歸後，他們中的大部分人都廻到了家鄕，卻又把護照放入抽屜以備不時之需。
It is something we can show off, or keep around for a rainy day to either entertain ourselves, work on, or reminisce what you were thinking that day when you wrote it.
詩歌可以用來炫耀，也可以伴隨左右以備不時之需——不論是爲了自娛自樂，還是爲了廻憶你寫詩時在想些什麽，或者是爲了接著那時的想法繼續思考。

He spoke for almost two hours on a cold and rainy day, without a hat or overcoat.
Now this is a rain gauge, and it's sitting on a roof of a building, and when the water falls into this gauge, it sends a signal to the logic unit of the computer, which immediately notifies the memory bank of the computer to seek out its instructions for a rainy day.
這是一個雨量測量器，安裝在一個樓房的,屋頂上，儅水流入到這個測量器，它就給計算機的邏輯部件發送一個信號，計算機立即通知內存條,爲下雨天找出相應的指令。
哈彿公開課 - 計算機科學課程節選
And making sure that folks have the opportunity and incentive to save for a home or college, for retirement or a rainy day is essential to that effort,".

It's very soothing and kind of introspective, and it's good for a rainy day.
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